1. Field of the Invention
This invention relates to analyzers for detecting the presence of formaldehyde in gaseous streams. More particularly, this invention relates to an automatic, portable analyzer for detecting the presence of formaldehyde in gaseous streams such as the exhausts from internal combustion engines used for natural gas compression and electrical power generation, the exhausts from turbines, and the exhausts from motor vehicles. The analyzer provides “near real-time” formaldehyde concentration measurements by completely automating the step wise procedures of the conventional Celanese wet chemistry method (EPA Draft Method 323; NCASI Method CI/SG/Pulp-94.02). In addition, the instrument eliminates the fragile glass components and the redundant sample impinger of the conventional wet chemistry test method while retaining the overall accuracy of the measurement.
2. Description of Related Art
The current state-of-the-art methods, such as the use of Fourier Transform Infrared (FTIR) devices, which use narrow absorption band signatures of species of interest, provide accurate formaldehyde detection. However, the capital cost (the order of $100,000), the extensive maintenance, lack of portability, and the required experience of a well-trained technician and spectroscopist make it unfeasible for periodic compliance monitoring, field application, and practical use.
An alternative known system for analyzing the amount of formaldehyde present in a gaseous stream is a dinitrophenylhydrazine (DNPH) coated sampler with solvent extraction and HPLC analysis. However, the DNPH method requires significant after sampling analysis and, thus, is not practical as a near real-time monitor. In addition, it requires solvent extractions and the use of expensive HPLC instruments. A related system involves the use of DNPH solutions in impingers and analysis of the impinger samples with HPLC analysis (EPA Method 11). However, DNPH solutions can be compromised by reactions with NOx species, particularly when the DNPH solution is not analyzed immediately.